New research from consumer watchdog Which? and mobile network monitoring firm Opensignal has found the UK’s worst postcodes for mobile signal, naming and shaming the specific areas of the country where finding bars is least reliable.
The postcode SA70 in the Welsh seaside town of Tenby is “the worst postcode for mobile network quality” in the UK according to Which?, who said mobile users in the area only got a “good” connection 54.3 percent of the time on average across the country’s four mobile networks of EE, O2, Three and Vodafone.
Three users in the area suffered the worst signal, only getting a solid connection 38 percent of the time, with EE and O2 faring better with 71 and 63 percent respectively.
Opensignal uses real-world usage data drawn from UK consumers’ mobiles, which is then used to find a percentage score that reflects the consistency of mobiles signal right down to specific postcodes. The results reflect signal data in 2025 up to and including August.
The second worst postcode for mobile network quality was LD1 in Llandrindod Wells, again a town in Wales, scoring just 54.8 percent. Three was again the worst network in this area.
The worst postcodes in England were TA5 in Taunton and TR43 in Truro, with 56 and 57.8 percent scores for network quality respectively. O2 was the least reliable networ in both areas with EE the best. Truro residents might despair at the fact two of the town’s other postcodes, TR27 and TR18, were also in the top 10 worst postcodes.
Postcodes in Dudley, Swansea, Medway and Ipswich also made it into that top 10.
Perhaps unsurprisingly, large cities such as London, Nottingham and Glasgow were among those that had the best mobile signal.
“This research shows just how dramatically the quality of mobile coverage can vary across the UK,” said Natalie Hitchins, Which? Head of Home Products and Services.
“Choosing the right provider can mean the difference between seamless coverage or constantly battling to make a call from the comfort of your own home.”
Tied for the best quality mobile coverage in the UK with a score of 87.8 percent was SE11 in London (Kensington and Vauxhall) and NG3 in Nottingham. All networks scored 85 percent reliability or higher.
Other London postcodes SW3 and Se27 scored well, as did postcodes in Sutton, Romford, Ilford and Glasgow.
Which? has updated its online mobile quality map that it says is informed by data from more than 17 million network tests from Opensignal users over the last 12 months. You can use the tool here to see which network is deemed to have the best coverage in your postcode.
Which? noted that mobile virtual network operators (MVNOs) such as Giffgaff and Smarty use one of the four main mobile networks to provide coverage, so users of these smaller firms should expect very similar results to the relevant corresponding network.
